This invention relates to methods of modulating an immune response, and in particular to methods of increasing an antigen-specific cytotoxic T lymphocyte response.
Immunostimulatory nucleic acid molecules were initially discovered in the mycobacterial genome as DNA sequences that selectively enhance NK cell activity (Yamamoto, et al. (1992) Microbiol. Immunol. 36:983-997). Uptake of mycobacterial DNA or has been shown to activate cells of the innate immune system, such as NK cells and macrophages and stimulating a type-1 like response (Roman, et al. (1997) Nature Med. 3:849-854). Further, administration of immunostimulatory nucleic acid molecules has been shown to induce B cell proliferation (Messina, et al. (1991) J. Immunol. 147:1759-1764), stimulate production of cytokines, such as interferons (IFNs), IL-12, IL-18 and TNF-xcex1 (Sparwasser, et al. (1998) Eur. J. Immunol. 28:2045-2054; Sparwasser, et al. (1997) Eur. J. Immunol. 27:1671-1679; Stacey, et al. (1996) J. Immunol. 157:2116-2122) and up-regulate co-stimulatory receptors (Martin-Orozco, et al. (1999) Int. Immun. 11:111-118; Sparwasser, et al. (1998) Eur. J. Immunol. 28:2045-2054) by these cells.
Cytotoxic T Lymphocytes (CTL) are critical effector cells in the control of cells infected with intracellular pathogens and in the control of MHC class I+ tumors. Induction of CTL is a primary goal of many vaccine strategies. Accumulating evidence indicates that one of the pathways of CTL priming in vivo is through xe2x80x9ccross-priming,xe2x80x9d which involves the uptake and re-presentation of soluble, exogenous antigens by bone marrow-derived antigen-presenting cells (APCs), e.g., dendritic cells. Depending on the activation state of the xe2x80x9ccross-presentingxe2x80x9d APC, responding T cells can either be activated or tolerized. The nature of the specific requirements for these disparate outcomes is currently a topic of intense interest, as elucidation of such would aid in the design of vaccines as well as in the modulation of anti-tumor CTL responses. Current models of cross-priming consist of two steps; a xe2x80x9clicensingxe2x80x9d interaction between antigen presenting cells (APC) and helper T cells (Th), followed by an activating interaction between xe2x80x9clicensedxe2x80x9d APC and cytotoxic T lymphocytes (CTL). Thus, in current models, there is a requirement for Th cells in cross-priming of CTL.
Immunodeficiency can arise from a variety of causes, including primary immunodeficiencies, e.g., due to a heritable defect; and acquired immunodeficiencies, e.g., due to cancer chemotherapy, or due to infection with a pathogen, e.g., human immunodeficiency virus. Immunodeficient individuals are more vulnerable to infectious diseases than individuals with healthy immune systems. Antibiotics can control bacterial infections, but long-term treatment with antibiotics is not without risk of adverse side effects. Control of intracellular pathogens, including viruses, bacteria, and protozoans, poses a greater challenge for treatment. Immunodeficient individuals may also be more vulnerable to growth of cancer cells than individuals with healthy immune systems. Treatment of these individuals with conventional anti-cancer therapeutic agents is not always feasible.
The current methodologies for inducing a CTL response include vaccines which use attenuated viruses or DNA vaccines. There is a need in the art for more effective ways of increasing an antigen-specific CTL response in an individual. Furthermore, there is a need in the art for alternative methods of enhancing immune functions in immunodeficient individuals. The present invention addresses these needs by providing methods for increasing cytotoxic T lymphocyte (CTL) activity. The methods are useful for increasing an antigen-specific CTL response in an individual to any soluble antigen. The methods are also useful for increasing an antigen-specific CTL response in CD4+-deficient individuals and individuals at risk for becoming CD4+ deficient.
The invention provides methods for T helper-independent activation of an antigen-specific cytotoxic T lymphocyte response in an individual. The methods generally involve administering to an individual an immunostimulatory nucleic acid molecule in an amount effective to increase an antigen-specific CTL response in the individual. The invention further provides methods for increasing chemokine secretion, which can block HIV infection.
The methods are useful for generating both a CTL response and a humoral response to a soluble exogenous antigen. Thus, an immunostimulatory nucleic acid molecule, when administered together with a soluble, exogenous antigen, results in cross-priming of CTLs. Therefore, the methods are useful in generating an immune response, particularly a CTL response, to a cell infected with an intracellular pathogen, or to a tumor cell expressing a tumor-specific or tumor-associated antigen.
The methods are also useful in treating individuals with a reduced number of functional CD4+ T cells (xe2x80x9cCD4+-deficient individualsxe2x80x9d or xe2x80x9cCD4+-low individualsxe2x80x9d) compared to normal individuals, e.g. individuals affected by an acquired or primary immunodeficiency, as well as those at risk for becoming immunodeficient.
The immunostimulatory nucleic acid molecules may be administered in a formulation alone, or together with an antigen, e.g., admixed or linked or conjugated to an antigen or antigenic epitope. In many embodiments, the antigen is a soluble, exogenous antigen. The methods are useful in stimulating, or increasing antigen-specific CTL activity to any of a variety of target antigens, e.g., an antigen expressed in a cell, or an antigen expressed on the surface of a cell or cell population. In some embodiments, methods are provided for increasing CTL activity toward pathogen-infected cells. In other embodiments, methods are provided for increasing CTL activity toward a tumor cell.
The invention further provides methods for increasing tumor-specific immunity in an individual. The methods generally involve administering to an individual an immunostimulatory nucleic acid molecule in an amount effective to increase tumor-specific immunity in an individual. The methods are useful to treat cancer, e.g., to inhibit the growth of cancer cells. The methods are also useful as a preventive measure, e.g., to inhibit the probability that cancerous cell growth will occur, or that a previously treated cancer will recur. The methods are particularly useful for decreasing a tumor load in a CD4+ T-cell deficient individual, and in individuals at risk for becoming CD4+ deficient.
The invention further provides methods of immunizing against and/or treating an infectious disease in an individual. The methods generally involve administering to an individual an immunostimulatory nucleic acid molecule in an amount effective to increase antigen-specific CTL activity. The methods are particularly useful in immunizing against and/or treating infectious diseases due to intracellular pathogens. The methods are also useful for treating infectious disease in a CD4+ T-cell deficient individual, and in individuals at risk for becoming CD4+ deficient.
The present invention further provides compositions and methods for increasing secretion of a chemokine from a eukaryotic cell, which in turn inhibits infection of a cell by pathogens that establish infection in a host, or cause disease by, interaction with a chemokine receptor. The methods generally involve contacting a cell with a composition comprising an immunostimulatory nucleic acid molecule. Accordingly, the invention further provides methods of reducing infection of a cell by a pathogen, comprising contacting a cell with an immunostimulatory nucleic acid molecule such that chemokine secretion is increased, and infection is reduced. Chemokine secretion may be antigen specific, where both immunostimulatory nucleic acid molecule and antigen are administered, or antigen non-specific, where immunostimulatory nucleic acid molecule is administered in the absence of exogenously provided antigen.
Immunostimulatory nucleic acid molecules induce secretion of chemokines that bind to chemokine receptors. Certain chemokine receptors are used by pathogenic microorganisms to enter and infect a cell. Increasing synthesis of such chemokines serves to competitively inhibit binding of the pathogenic microorganism to the chemokine receptor. Accordingly, in further aspects, the present invention provides compositions and methods for increasing secretion of a chemokine from a eukaryotic cell, which in turn inhibits infection of a cell by pathogens that establish infection in a host, or cause disease by, interaction with a chemokine receptor. The methods generally involve contacting a cell with a composition comprising an immunostimulatory nucleic acid molecule. Accordingly, the invention further provides methods of reducing infection of a cell by a pathogen, comprising contacting a cell with an immunostimulatory nucleic acid molecule such that chemokine secretion is increased, and infection is reduced. Chemokine secretion may be antigen specific, where both immunostimulatory nucleic acid molecule and antigen are administered, or antigen non-specific, where immunostimulatory nucleic acid molecule is administered in the absence of exogenously provided antigen.
These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the invention as more fully described below.